CVE-2026-2880
A vulnerability in @fastify/middie versions < 9.2.0 can result in authentication/authorization bypass when using path-scoped middleware (for example, app.use('/secret', auth)).
Does this matter?
High impact if exploited, but EPSS currently rates exploitation as unlikely (0.39%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit.
Description
A vulnerability in @fastify/middie versions < 9.2.0 can result in authentication/authorization bypass when using path-scoped middleware (for example, app.use('/secret', auth)). When Fastify router normalization options are enabled (such as ignoreDuplicateSlashes, useSemicolonDelimiter, and related trailing-slash behavior), crafted request paths may bypass middleware checks while still being routed to protected handlers.
- CVSS 4.0
- 8.2 HIGHCVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/M
- EPSS
- 0.39% probability · 32th percentile
- CISA KEV
- Not listed
- Weakness
- CWE-20
- Affected
- fastify/fastify\/middie
- Source
- ce714d77-add3-4f53-aff5-83d477b104bb
References
- https://github.com/fastify/middie/security/advisories/GHSA-8p85-9qpw-fwgwMitigation, Vendor Advisory
Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.